1. Field of the Invention
The present invention relates to a torque sensor in which a torque applied or transmitted to a torque transmission shaft is detected in a non-contact manner by use of a so-called stress-magnetic effect in which a member made of a magnetic material exhibits a change in a magnetic permeability when an external stress is applied to the magnetic material member, and also to a multifunctional torque detection device in which a power (or horse power) is operationally detected or determined by detecting the rotation (or r.p.m.) of the torque transmission shaft in a non-contact relation with the torque transmission shaft by use of a magnetic means simultaneously with the detection of the torque.
2. Description of the Related Art
Recently, the development of sensors for mechanical quantities using the stress-magnetic effect has come into the lime light. For example, torque sensors using this principle have been disclosed by U.S. Pat. Nos. 4,823,617, JP-A-61-312250, and so on.
The construction of this kind of conventional torque sensor will now be explained in reference to FIG. 13.
In the figure, reference numeral 61 denotes a torque transmission shaft, numerals 62a and 62b amorphous magnetic alloy members having magnetostriction, numerals 63a and 63b coils, and numeral 64 a differential detection circuit. The torque transmission shaft 61 and the amorphous magnetic alloy members 62a and 62b are bonded to each other by a bonding agent such as a polyimide series resin, and the bonding agent is cured at a temperature higher than a working temperature region of the sensor so that an in-plane internal compressive stress is applied to the amorphous magnetic alloy members 62a and 62b due to a difference in linear thermal expansion coefficient between the torque transmission shaft 61 and the amorphous magnetic alloy members 62a and 62b. The coils 63a and 63b are wound centering around the torque transmission shaft 61 and are connected to the differential output or detection circuit 64.
When a torque is applied to the torque transmission shaft 61, strains are generated in the amorphous magnetic alloy members 62a and 62b. Thereby, a magnetic permeability changes due to a stress-magnetic effect. As a result, the inductances of the coils 63a and 63b change. For example, in the case of a right-handed (or right-twisted) torque, the inductance of the coil 63a becomes large and the inductance of the coil 63b becomes small. This change is detected by the differential detection circuit 64, thereby permitting simultaneous detection of the magnitude and direction of the applied torque.
In such a conventional torque sensor, the magnitude and direction of a torque transmitted to the torque transmission shaft 61 can be detected. However, in the case where a power (or horse power) is to be determined, the rotation (or r.p.m.) of the shaft 61 necessary for the determination of the power must be detected by means of an additionally provided rotation sensor. Thus, the conventional torque sensor has a drawback that the power cannot be detected by the torque sensor itself.